Field of the Invention
The invention relates in general to an electronic signal receiving apparatus, and more particularly, to a technology for estimating carrier frequency offset in an electronic signal receiving apparatus.
Description of the Related Art
Various types of communication systems get more and more popular as related technologies in the electronics field continue to advance. Each of a transmitter and a receiver of a communication system is provided with at least one oscillation signal source (e.g., a quartz oscillator) that provides a clock signal as a basis for circuit operations. During an operation process, clock frequencies of the transmitter and the receiver need to achieve certain consistency in order to have the receiver correctly parse signals sent from the transmitter. If the frequency of a clock signal that the receiver adopts for down-converting an input signal differs from the frequency of a clock signal that the transmitter adopts for up-converting a baseband signal, such issue is commonly referred to as carrier frequency offset at the receiver. The carrier frequency offset may lead to inter-carrier interference, causing negative effects such as degraded system performance of the receiver, and the receiver may even become incapable of parsing its input signal in some severe cases.
A usual cause of the carrier frequency offset is mismatch between respective oscillators at a transmitter and a receiver. In practice, the transmitter and receiver may be fabricated by different manufactures based on different hardware of different specifications. Thus, exact matching between the oscillators at these two ends is extremely difficult, and so the receiver is usually designed with a mechanism for compensating carrier frequency offset. In general, a receiver needs to first correctly estimate the value of the carrier frequency offset before frequency offset compensation can be effectively conducted.